[LeetCode] Longest Valid Parentheses 最长有效括号

Given a string containing just the characters ‘(‘ and ‘)‘, find the length of the longest valid (well-formed) parentheses substring.

For "(()", the longest valid parentheses substring is "()", which has length = 2.

Another example is ")()())", where the longest valid parentheses substring is "()()", which has length = 4.

这道求最长有效括号比之前那道Valid Parentheses 验证括号难度要大一些,这里我们还是借助栈来求解,需要定义个start变量来记录合法括号串的起始位置,我们遍历字符串,如果遇到左括号,则将当前下标压入栈,如果遇到右括号,如果当前栈为空,则将下一个坐标位置记录到start,如果栈不为空,则将栈顶元素取出,此时若栈为空,则更新结果和i - start + 1中的较大值,否则更新结果和i - 栈顶元素中的较大值,代码如下:

class Solution {
public:
    int longestValidParentheses(string s) {
        int res = 0, start = 0;
        stack<int> m;
        for (int i = 0; i < s.size(); ++i) {
            if (s[i] == ‘(‘) m.push(i);
            else if (s[i] == ‘)‘) {
                if (m.empty()) start = i + 1;
                else {
                    m.pop();
                    res = m.empty() ? max(res, i - start + 1) : max(res, i - m.top());
                }
            }
        }
        return res;
    }
};

还有一种利用动态规划Dynamic Programming的解法,可参见网友喜刷刷的博客

时间: 2024-10-10 04:38:02

[LeetCode] Longest Valid Parentheses 最长有效括号的相关文章

[LeetCode] 32. Longest Valid Parentheses 最长有效括号

Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring. For "(()", the longest valid parentheses substring is "()", which has length = 2. Another example is &

[leetcode]32. Longest Valid Parentheses最长合法括号子串

Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring. Example 1: Input: "(()" Output: 2 Explanation: The longest valid parentheses substring is "()" Example

[LeetCode]Longest Valid Parentheses, 解题报告

题目 Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring. For "(()", the longest valid parentheses substring is "()", which has length = 2. Another example i

LeetCode: Longest Valid Parentheses [031]

0.下载安装Opencv,当前版本为249. 1.下载Python,当前OPencv版本为249,不过其支持的最新版本的Python为2.7,所以可以下载276版本. 2.下载numpy,开始我使用了1.6,没有通过,错误如图.下载了最新的1.8.1版本. 3.将Opencv安装目录下opencv\build\python\2.7\x86中的cv2.pyd复制到python安装目录Lib\site-packages下. 4.找到opencv源文件内的draw.py运行. LeetCode: Lo

leetCode 32.Longest Valid Parentheses (有效的最大括号) 解题思路和方法

Longest Valid Parentheses Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring. For "(()", the longest valid parentheses substring is "()", which has length

[LeetCode] Longest Valid Parentheses 解题思路

Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring. For "(()", the longest valid parentheses substring is "()", which has length = 2. Another example is &

LeetCode: Longest Valid Parentheses O(n)时间 O(1)空间

题目: Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring. For "(()", the longest valid parentheses substring is "()", which has length = 2. Another example

LeetCode Longest Valid Parentheses

Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring. For "(()", the longest valid parentheses substring is "()", which has length = 2. Another example is &

[LeetCode] Longest Valid Parentheses 动态规划

Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring. For "(()", the longest valid parentheses substring is "()", which has length = 2. Another example is &